I am no professional machinest, but there is really not that much " meat" on the Excal. The parallel tubes under the bolt have a wall thickness around .100" and even in owners manual (on disk) it mentions only removing something like .040" or .050" ( I am getting that from memory, so not completely sure of that). It is also has a curve of the of the tube itself. So if you want anything really nice there, you want to make sure who is doing it is very careful, or is doing it by CNC.
There is still other thinks that can be done, just be creative within the limits of what is there.
I would have like to have done more to mine, but its always easier to say "what if"?
AKA is very flexible on having you get the milling done by someone else. They take some special requests and make them no problem. They did a lot for me!